Heated drying roller



Feb. 13, 1951 H. HARRISON HEATED DRYING ROLLER Filed July 26, 1947 FIG.4.

FIG.3.

FIG. 5.

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W (H 0 Z w rins :the drum and "heating means Patented Feb. 13, 1951HEATED DRYING ROLLER Henry Harrison, Rochester, N. Y., assignor toEastman Kodak Company, Rochester, N. Y., a corporation of New JerseyApplication July 26, 1947, Serial No. 763,923

3 Claims. 1

The present invention relates to drying drums for'rollers, and moreparticularly to a heating means therefor.

Drying drums used for drying photographic prints are large and slowurning, and are difflcult to make since they are usually formed ofextruded copper to avoid joints. Such drums are subjected to corrosionwhen heated with water or steam. In order to avoid such corrosion, somedrums are heated by electric coils or similar means positioned withinthe drum. Such heating arrangements do not however provide a uniformheating of the drum, and the heating means themselves arehigh-temperature units, the disadvantage of which will be readilyapparent to those in the art.

' In order to overcome these disadvantages, the present inventionprovides a drum which is formed of a material having a high magneticpermeability. A means is provided for producing a low-frequency magneticflux, and this means is linked with the drum to provide a magnetic fluxpath of low reluctance. This flux produce hysteresis and eddy currentlosses which serve to heat the drum uniformly and to the desiredtemperature and without the use of high-temperature heating means.

f'yThe present invention has, therefore, as its in which the coil onlyis used and the drum con- I stitutes theentire flux path; and

principal object the provision of an arrangement for heating a dryingdrum by means of hysteresis and eddy current losses.

"A further object of the invention is the provision of an arrangement inwhich the drum itself forms part ofthe magnetic flux path.

" -Yet another object of the invention is the use I of a low-frequencyalternating magnetic flux for heating the-drum.

Still another object of the invention is the provision of an arrangementfor heating the drying drum which is simple, and which does not employhigh-temperature heating means.

To these and other ends, the invention resides in certain improvementsand combinations of parts, all as will be hereinafter more fullydescribed, the novel features being pointed out in the claims at the endof the specification.

In the drawings:

1;, Fig. Iris a transverse vertical sectional view through a dryingdrum, showing one embodiment of a heating means constructed in accord-;ance with the present invention;

Fig. 2 is a longitudinal sectional view through illustrated in Fig.

"1 on line 2-2 thereof;

Fig. 3 is a perspective view of the drum and core illustrated in Figs. 1and 2 with part of the dr-u-m-broken away to show more clearly thearrangement of the parts;

Fig. 4 is a vertical sectional view showing a modified arrangement ofdrum and heating coil Fig. 5 is a sectional view through the drumandcoil illustrated in Fig. 4 and on line 5"-5 thereof showing the relationof the parts.

Similar reference numerals throughout thevarious views indicate the sameparts.

The present invention relates to an arrange ment which utilizeshysteresis and eddy current losses for heating a drying drum. To securethis result, a drum is formed of a material having a high magneticpermeability and has posi-' tioned therein a laminated core whichis'linked to the drum to provide a flux path of low reluctance. Alow-frequency alternating current is supplied to a coil associated withthe core to produce an alternating magnetic flux in the flux paththrough the core and drum. The core is laminated so that the lossesoccur principally in the drum rather than in the core so as toeifectively heat the drum uniformly and without the use ofhigh-temperature heating elements.

Figs. 1 to 3 show one embodiment of the invention in which is provided anovel print drying drum l'l formed of a material of high magneticpermeability, such as unannealed but stress-relieved cast iron, cold.rolled steel, or high carbon steel. The drum is supported on a pair ofrollers l2 one of which may be driven to rotate the drum at the desiredspeed. Suit able aprons, not shown in Figs. 1 and 3, cooperate with thedrum to hold the print in contact therewith during the drying operation.If desired, the drum may be provided with a suitable coating, such ascopper (chromium-plated).

A laminated iron core which in the present instance is H-shaped, isprovided with spaced legs l3 and I4 which are positioned adjacent theinner surface of the drum, and a cross or connecting member I5 on whichis positioned a winding or coil l5 adapted to be connected to a sourceof low-frequency alternating current, not shown. By low frequency ismeant frequency below cycles per second. As the core and drum are iron,and the air spaces between the legs I3 and i4 and the drum are quitesmall, the core forms with the drum a magnetic flux path of lowreluctance. When low-ire quency alternating current is applied to thewinding l5, an alternating magnetic flux is produced in the magneticflux path through the core and drum. As the same flux passes boththrough the core and drum, the cross-sectional area of the core is equalto the area of the drum carrying the fluxnamely, the drum -lengthmultiplied by twice the drum thickness.

The alternating magnetic flux in the flux path gives rise to hysteresisand eddy current losses, the latter of which are larger.- These lossescause a heating action to take place, and as the core is laminated, thelosses occur principally in the drum so that the heat resulting fromsuch losses is utilized to heat the drum to the proper temperature. Asthe drum itself forms part of the magnetic flux path, the heatingresulting from such losses serves to heat the drum uniformly. The actualamount of power necessary to heat the drum to the desired temperaturewill vary with the size and composition of the drum, but with a castiron drum 4' in diameter and 24" long and A;" thick, 5000 watts arerequired. This, however, is about the maximum power which can bedelivered at 60 cycles to a drum of this size.

As the major part of the losses occur directly in the material of thedrum, substantially all the heat resulting from such losses is utilizedfor heating the drum. Also the heating is produced without the use ofhigh-temperature r corroding heating means, and the structure isextremely simple. The core and the winding may be carried by end plates,not shown, which close the end of the drum. These plates are preferablystationary so that the core and winding remain in fixed position withinthe drum.

While the core as shown is H-shaped, other shapes, such as U-shapedcores, may be used. The fundamental requirement is that the core formwith the drum a magnetic flux path of low reluctance. While the use of acore is preferred, the core may be eliminated but the winding or coilwhich provides a magneto-motive force must be linked with the iron fluxpath of the drum. In the arrangement in Figs. 1 to 3, the drum itselfforms only a part of the flux path, but in the embodiment shown in Figs.5 and 6, the drum constitutes the entire flux path.

In this latter arrangement, the drum H has wound therearound a hollowwinding or core through which a portion of the drum extends and moves sothat the drum will constitute a core for the winding. The latter isconnected to 110-volt, 60-cycle source of power and when the latter isapplied to the coil 20 an alternating magnetic flux is induced in thedrum which now forms the complete flux path. As in a previouslydiscussed arrangement, illustrated in Figs. 1 and 3, this alternatingmagnetic flux causes hysteresis and eddy current losses to develop inthe drum and these losses serve to heat the drum to the propertemperature. Parts in Figs. 4 and 5 which correspond to those in Figs. 1to 3 are designated by the same numerals.

Thus in both embodiments, the drum itself forms a portion at least ofthe magnetic flux path, and when the path is subjected to a lowfrequency alternating magnetic flux, hysteresis and eddy current lossesresult and these losses are utilized directly to heat the drum. Suchheating means is low temperature and produces a uniform heating of thedrum.

While certain embodiments of the invention have been disclosed, it is tobe understood that the inventive idea may be carried out in a number ofways. This application is, therefore, not to be limited to the precisedetails described, but is intended to cover all variations andmodifications thereof falling within the scope of the appended claims.

What I claim is:

'1. A drying apparatus comprising, in combination, a rotatably mountedcylindrical drum formed of a material of high magnetic permeability, astationary laminated core of high magnetic permeability positionedradially within said drum in inductive relation therewith and havingportions thereof commensurate in length with said drum, said portionsbeing positioned adjacent but physically disconnected from said drum, anelectrically conducting coil positioned on another portion of said coreand supplied directly with low frequency alternating current of at leastvolts potential, the flow of current through said coil producingmagnetic flux in a low reluctance path a part of which is in the core ina direction radially of said drum and another part of which is in acircumferential direction through said drum.

2. Drying apparatus comprising, in combination, a rotating hollow drumhaving a cylindrical portion formed of a material of high magneticpermeability, an H-shaped laminated stationary core of high magneticpermeability positioned radially of said drum in inductive relationthere.- with and having legs extending axially of and commensurate inlength with said drum, said legs being position adjacent but spacedslightly from and disconnected physically from said drum, a cross-memberextending radially of said drum and connecting said legs, a coil woundon said cross-member and supplied directly with low frequencyalternating current of at least 110 volts potential to set up magneticflux in two independent and separate low reluctance paths both of whichare through the laminated core and each of which is in a circumferentialdirection through the cylindrical portion of said drum. 1

3. A drying apparatus comprising, in combination, an H-shaped laminatedcore of high magnetic permeability, an electrically conducting coilwound on the cross arm of said core, a rotating hollow drum having acylindrical portion closely surrounding said core in inductive relationtherewith and with the axis of the drum parallel to the laterals of theH, and the drum immediately adjacent said laterals, said drum beingformed of a material of high magnetic permeability and havingapproximately the same length as said laterals, said coil being supplieddirectly with low frequency alternating current of at least 110 voltspotential, the flow of current through said coil setting up magneticflux in said core the return path of which is in a circumferentialdirection through the cylindrical portion of said drum.

HENRY HARRISON.

REFERENCES CITED The following references are of record in the file ofthis patent:

UNITED STATES PATENTS

